Centrifuge construction

ABSTRACT

A drum for a centrifuge is mounted for rotation about its longitudinal axis and has a circumferential wall and an outlet end. It is composed of a plurality of slightly spaced axially adjacent rings each of which has an outer circumferential surface and an inner circumferential surface with the latter continuously diverging in direction towards the opening. Each of the rings has a minimal inner diameter greater than the minimal inner diameter of the respective axially preceding ring and an axial end face facing said outlet end and extending from the inner to the outer circumferential surface. Admitting means admits mixture to be separated into the drum, and drive means rotates the drum about its axis.

United States atetit Von Gronow Feb. 1, 1972 OTHER PUBLICATIONS German Printed Publication, Buddeberg, W., K22224, Dec. 29, 1955 Primary Examiner-Patrick D. Lawson Assistant ExaminerGeorge H. Krizmanich Attorney-Michael S. Striker [57] ABSTRACT A drum for a centrifuge is mounted for rotation about its longitudinal axis and has a circumferential wall and an outlet end. It is composed of a plurality of slightly spaced axially adjacent rings each of which has an outer circumferential surface and an inner circumferential surface with the latter continuously diverging in direction towards the opening. Each of the rings has a minimal inner diameter greater than the minimal inner diameter of the respective axially preceding ring and an axial end face facing said outlet end and extending from the inner to the outer circumferential surface. Admitting means admits mixture to be separated into the drum, and drive means rotates the drum about its axis.

12 Claims, 5 Drawing Figures DRIVE MER/l/S CENTRIFUGE CONSTRUCTION BACKGROUND OF THE INVENTION The present invention relates generally to centrifuges, and more particularly to centrifuges for separating mixtures of liquid and solid phases.

Centrifuges are known for separating mixtures of solid and liquid phases, for instance for separating synthetic plastic granules from water or other liquid with which they are admixed for any one of a variety of different reasons. One such construction known from German allowed patent application DAS 1,432,821. This device utilizes a drum the circumferential wall of which is composed of a plurality of discrete axially arrayed rings each of which has an inner surface and an outer surface which continuously taper in opposite direction and which are connected with one another in the direction towards the outlet end of the drum by a continuously curved edge. When a suspension is introduced into such a drum and the latter is rotated about its axis, the solid particles of the suspension are deflected as they move over the curved edge and proceed in free flight to the next-following ring, that is to the inner circumferential surface thereof. Because of the centrifugal force resulting from rotation of the drum, the suspension is distributed over the inner circumferential surface of the rings in form of a film or layer, and the liquid phase is successivelyand retained by adhesion on the outer circumferential surfaceseparated from the particles as the particles move from the inner circumferential surface of one to the inner circumferential surface of the axially adjacent next ring, until the particles finally are ejected from the terminal 1 of the rings at the outlet end of the drum.

This centrifuge construction has several very advantageous features. Not only does it provide for excellent separation of the liquid and solid phases, but also its throughput capacity is considerable. In addition, is the fact that it can be utilized for classification of solid particles of different size because solid particles of different size will be ejected at different locations depending upon their size and can thus be separately collected.

However, this known construction has one disadvantage. Specifically, if the centrifuge is to be used primarily for separation of solid and liquid phases and a classification effect is of no or subordinate importance, such as the separation of water from synthetic plastic granules, relatively complicated construction of this prior art device-particularly with respect to the configuration of the individual rings-is too expensive for economic use.

SUMMARY OF THE INVENTION It is accordingly, an object of the present invention to provide an improved centrifuge construction.

More particularly, it is an object of the present invention to provide a centrifuge for the separation of solid and liquid phases.

Still more particularly, it is an object of the present invention to provide an improved centrifuge for the above purposes but which is simpler in its construction than the one discussed above with respect to the prior art.

In pursuance of the above objects, and others which will become apparent hereinafter, one feature of the invention resides in a centrifuge for separating mixtures of liquid and solid phases, which centrifuge comprises, briefly stated, a drum mounted for rotation about its longitudinal axis and having a circumferential wall and an outlet end, with the wall being composed of a plurality of axially adjacent but slightly spaced rings and each has an outer circumferential surface and an inner circumferential surface with the latter continuously diverging in direction towards the outlet end. Each of the rings has a minimum inner diameter, greater than the maximum inner diameter of the respective axially preceding ring and an axial end face facing the outlet end and extending from the inner to the outer circumferential surface of the respective ring. Admitting means is provided for admitting mixture to be separated into the drum, and drive means serve to rotate the drum about its axis.

According to the invention the axial end faces ofthe respective rings are either planar and located in a plane normal to the axis of the rotation ofthe drum, or they continuously convexly diverge from the inner to the outer circumferential surface of the respective ring.

With the construction according to the present invention the separation of liquid from solid phase takes place only at one specific region of each ring, namely either at the juncture between the inner circumferential surface of each ring and the associated axial end face if the latter is planar, or on the axial end face itself if the latter is continuously convexly diverging in the manner indicated above. Thus, unlike the prior art construction described above, there is no outer surface on which further separation takes place as a result of adhesion of the liquid, and the centrifuge is thus not only lighter in weight but also simpler to produce, both from an engineering standpoint and from a manufacturing point of view. Despite the fact that the centrifuge according to the present invention is intended predominantly for the separation of liquid and solid phases, it has been found that even so the construction can still be used for a certain amount of classification as to size. Such classification occurs if a certain quantity of the solid particles does not move in free flow from the axial end face of one ring to the inner circumferential surface of the next adjacent ring, as is normally the case, but instead is ejected through the gap between the rings.

It is advantageous although not necessary that the axial end face define with the outer circumferential surface of the respective ring a sharp edge. This not only makes for a simpler manufacturing procedure but, if the axial end face is continuously convexly tapered in radially outward direction towards the outer circumferential surface, the provision of this sharp edge further enhances the separating effect.

A particularly simple manner of constructing the rings which make up the drum, provides for making the rings of sheet material. In this case it is highly advantageous if the rings are sections which are cut out of a conical hollow sheet material metal. Care must of course be taken that the thus produced rings meet the requirement of the invention which calls for the minimum inner diameter of each ring to be greater than the next inner diameter of the axially preceding ring.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a fragmentary axial section through a centrifuge embodying the invention;

FIG. 2 is a fragmentary axially sectioned detailed view on an enlarged scale illustrating a further embodiment of the invention;

FIG. 3 is a fragmentary axial section illustrating yet another embodiment of the invention;

FIG. 4 is an analogous view to FIG. 3 but illustrating still an additional embodiment of the invention; and

FIG. 5 is a view analogous to FIG. 2 but of yet an additional embodiment.

DESCRIPTION OF SPECIFIC EMBODIMENTS Discussing now the drawing in detail, and firstly FIG. 1 thereof it will be seen that reference numeral 1 identifies a stationary admitting means or inlet conduit through which a mixture of solid and liquid phases which are to be separated is introduced into the centrifuge. The centrifuge drum is identified with reference numeral 2 and comprises in the illustrate embodiment six axially adjacent rings, identified with reference numerals 38. Ring 3 constitutes the body of the drum and is provided with a transversely extending end wall 9 onto which the mixture is discharged from the conduit 1. The outlet end of the drum 2 is open and illustrated in FIG. 1.

Each of the rings 38 has an inner circumferential surface and an outer circumferential surface 11. In the embodiment of FIG. I the axial end face of each ring which faces the next-succeeding ring or, as it might be expressed, which faces towards the outlet end of the drum, convexly curves or diverges from the inner circumferential surface 10 to the outer circumferential surface 11 of the respective ring 38. The axial end faces are identified with reference numeral 12 and it will be seen that they define a sharp edge with the respective outer circumferential surface 11.

Mixture admitted onto the bottom wall 9 via the conduit 1 first moves under the influence of centrifugal force-as the drum 2 is rotated about its axis of rotation which is defined by the shaft 21 which in turn is adapted to be rotated via the diagrammatically illustrated drive means-onto the inner circumferential surface 10 of the ring 3. It moves upwardly over this inner circumferential surface 10 which diverges continuously in direction towards the upper outlet end of the drum 2. It need hardly be emphasized that the axis of rotation is upright. As soon as the mixture reaches the axial end face 12 of the ring 3 the liquid phase continues to flow-under the influence of adhesionover the axial end face until it reaches the radially outermost edge thereof, that is the juncture of the axial end face with the outer circumferential surface 11 of the ring 3. From this edge it is flung off. The solid phase, however, is flung off in the axial end face 12 of the ring 3 at or before the time it has traversed the distance between the inner circumferential surface 10 and the outer circumferential surface 11 of the ring 3 and moves in free flight onto the inner circumferential surface 10 of the next-following ring 4. This is a result of the cooperation of the inertia and centrifugal forces acting on the solid phase. On each successive ring-that is the rings 4, 5, 6, 7this process is repeated, and each gap between two successive rings additional liquid phase is removed until the solid phase is dry by the time it reaches the axial end face 12 of the terminal ring 8. The term dry" was employed herein is intended of course not to designate an absolute but to specify that the solid phase is relatively dry, having been freed of the liquid phase.

In the embodiment of FIG. 1 the rings 3-8 are each connected to one of the annular members 13-18 and the latter in turn are mounted on both threaded rods 19 via the illustrated retaining nuts (no reference numerals were designated). Nuts 19 are in turn secured to a wrenched disk 20 which is mounted on the drive shaft 21 for rotation with the latter. Depending upon the particular composition of a mixture to be separated into its liquid and solid constituent phases, it may be desirable to vary the spacing or gaps between axially adjacent ones of the rings 3-8; in the construction according to FIG. 1, this can be accomplished very readily by repositioning the nuts holding the annular members 13-18, lengthwise of the rods 19. It will be appreciated that while only one side of the drum has been shown in section, the opposite side is mirror-symmetrical and therefore needed not be specifically described.

The embodiment illustrated in FIG. 2 differs from that of FIG. 1 in that two axially adjacent rings 3a and 4a are illustrated and with the axial end face 12a of the ring 3a-facing the ring ta-being planar and located in a plane normal to the axis of rotation of the rings and thereby of the drum. The end face 12a thus defines sharp edges both at its junction with the inner circumferential surface 10a and the outer circumferential surface 11a. The sharp edge at the juncture of the surface 10a and the end face 120 is identified with reference numeral 25 and that at the juncture between end face 12a and the outer circumferential surface 11a is identified by reference numeral 27. The separating effect, that is the separation of liquid and solid phases of the mixture occurs in this embodiment at the edge 25 and at which the solid parti cles are flung off to traverse approximately the path identified by the arrow 26 and to come to rest on inner circumferential surface of the ring 4a. Of course, the other rings necessary to provide a drum can be constructed in the same manner, and it is also possible to provide some rings with axial end face 12 in FIG. I, and others with the axial end face 12a of FIG. 2. The liquid phase again passes over the axial end face to the sharp edge 27 form which it is flung off.

In the embodiment illustrated in FIG. 3, where again only one side of a drum is shown, the rings are identified with reference numeral 29 and correspond to those illustrated in FIG. 1, or those illustrated in FIG. 2. The embodiment in FIG. 3 utilizes a preliminary separation, means for which are shown in this Figure. Here the mixture admitted again through the conduit 1 descends down to the bottom wall of the drum as in the preceding embodiments, except that this bottom wall is the bottom wall of a rotating screen drum configurated as a conical element 30 and provided with annular circumferentially extending reinforcing members 31 which are diagrammatically illustrated. The mixture advances upwardly already in a surface of the screen drum 30, with some of the liquid phase already escaping through the mesh of the screen drum 30, into a space defined outwardly thereof by a cylindrical jacket 36 which is provided with apertures through which separate liquid phase can escape. These apertures are identified with reference numeral 37. The remaining liquid phase and the solid phase then moves unto the inner circumferential surface of the first or lowermost ring 29 which corresponds to ring 3 of FIG. 1, and from there the separation proceeds as described with reference to FIG. 1. The actual drum composed of the rings 29 and corresponding to the drum 2 of FIG. 1, is identified diagrammatically with reference numeral 35 in FIG. 3.

The embodiment in FIG. 4 differs form that in FIG. 3 in only one respect, namely, in that the screen drum 32, reinforced by the annular circumferential reinforcing elements 33 is not conical but instead diverges arcuately towards the drum 35. Neither the screen drum 3!) nor the screen drum 32 is self-supporting. The embodiments of FIGS. 3 and 4 have in common a conical annular guide member 38 which surrounds the lower end of the conduit 1 and defines a narrow gap between its outer circumferential edge and the inner circumferential surface of the lowest ring 29 so that the mixture which moves upwardly over the screen drums 30 or 33 is guided by the downwardly facing surface of the guide member 38 and must necessarily contact the inner circumferential surface of the lowermost ring 29 at or just before the juncture therewith of the axial end face of the lowermost ring 29, at whichjuncture the first separation in the drum 35 occurs. Reference numeral 34 identifies the drive shaft corresponding to the drive shaft 21 in FIG. 1, to which the jacket member 36 is connected for rotation with the same. The screen drums 30 and 32 are advantageously both mounted as to be readily movable for inspection, cleaning and/or replacement.

It will be appreciated that it is important for the minimum inner diameter of each of the rings to be greater than the maximum inner diameter of the respectively preceding ring, keeping in mind that the inner circumferential surface (and therefore diameter) of each ring diverges continuously in direction toward the next successive ring (and therefore toward the outlet end of the drum).

In the preceding embodiments the outer circumferential surface of each ring conveys or tapers axially of the ring in direction away from the outlet end of the centrifuge drum.

The embodiment of FIG. 5, however, shows that the outer surface may also be constant, that is that it neither diverges nor conveys axially of the respective ring. This embodiment is otherwise similar to the embodiment illustrated in FIG. 2 and may of course also include features of the other disclosed embodiments.

It will be understood that each of the elements described above, or two or more together may also find a useful applica tion in other types of applications differing from the types described above.

While the invention has been illustrated and described as embodied in a centrifuge construction, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

Iclaim:

l. A centrifuge for separating mixtures of liquid and solid phases, comprising a drum mounted for rotation about its longitudinal axis and having a circumferential wall and an outlet end, said wall being composed ofa plurality of axially adjacent but slightly spaced rings each of which has an inner circumferential surface which diverges continuously in direction towards said outlet end, said rings each having in direction towards said outlet end a minimum inner diameter greater than the maximum inner diameter of the respective axially preceding ring and an axial end face facing said outlet end and extending from said inner to said outer circumferential surface; admitting means for admitting mixture to be separated into said drum; and drive means for rotating said drum about said axis whereby the liquid phase moves along the respective inner circumferential surfaces and thence the associated axial end faces by adhesion so as to be flung off in the region of the respective outer circumferential surfaces, whereas the solid phase jumps the spacing between successive rings and advances toward said outlet end.

2. A centrifuge as defined in claim I, wherein said axial end face is planar and located in a plane transverse to said axis.

3. A centrifuge as defined in claim 2, wherein said plane extends normal to said axis.

4. A centrifuge as defined in claim I, wherein said axial end face continuously convexly diverges from said inner to said outer circumferential surface.

5. A centrifuge as defined in claim I, wherein said rings are of constant wall thickness between said inner and outer circumferential surfaces thereof.

6. A centrifuge as defined in claim 1, wherein the wall thickness of the respective rings between the respective inner and outer circumferential surfaces decreases axially of said drum in direction toward said outlet end.

7. A centrifuge as defined in claim 6, wherein said wall thickness decreases continuously.

8. A centrifuge as defined in claim I, wherein said axial end face and said outer circumferential surface define a sharp edge at their juncture with one another.

9. A centrifuge as defined in claim I, wherein said rings are composed of sheet material.

10. A centrifuge as defined in claim 9, wherein said rings are severed sections of a conically configurated sheet material member.

11. A centrifuge as defined in claim 1, wherein said outer circumferential surface of said rings is diminishing in opposite direction towards said outlet end.

12 A centrifuge as defined in claim 1, wherein said outer circumferential surface of said rings has a constant diameter over the length of each of said rings. 

1. A centrifuge for separating mixtures of liquid and solid phases, comprising a drum mounted for rotation about its longitudinal axis and having a circumferential wall and an outlet end, said wall being composed of a plurality of axially adjacent but slightly spaced rings each of which has an inner circumferential surface which diverges continuously in direction towards said outlet end, said rings each having in direction towards said outlet end a minimum inner diameter greater than the maximum inner diameter of the respective axially preceding ring and an axial end face facing said outlet end and extending from said inner to said outer circumferential surface; admitting means for admitting mixture to be separated into said drum; and drive means for rotating said drum about said axis whereby the liquid phase moves along the respective inner circumferential surfaces and thence the associated axial end faces by adhesion so as to be flung off in the region of the respective oUter circumferential surfaces, whereas the solid phase jumps the spacing between successive rings and advances toward said outlet end.
 2. A centrifuge as defined in claim 1, wherein said axial end face is planar and located in a plane transverse to said axis.
 3. A centrifuge as defined in claim 2, wherein said plane extends normal to said axis.
 4. A centrifuge as defined in claim 1, wherein said axial end face continuously convexly diverges from said inner to said outer circumferential surface.
 5. A centrifuge as defined in claim 1, wherein said rings are of constant wall thickness between said inner and outer circumferential surfaces thereof.
 6. A centrifuge as defined in claim 1, wherein the wall thickness of the respective rings between the respective inner and outer circumferential surfaces decreases axially of said drum in direction toward said outlet end.
 7. A centrifuge as defined in claim 6, wherein said wall thickness decreases continuously.
 8. A centrifuge as defined in claim 1, wherein said axial end face and said outer circumferential surface define a sharp edge at their juncture with one another.
 9. A centrifuge as defined in claim 1, wherein said rings are composed of sheet material.
 10. A centrifuge as defined in claim 9, wherein said rings are severed sections of a conically configurated sheet material member.
 11. A centrifuge as defined in claim 1, wherein said outer circumferential surface of said rings is diminishing in opposite direction towards said outlet end.
 12. A centrifuge as defined in claim 1, wherein said outer circumferential surface of said rings has a constant diameter over the length of each of said rings. 